/* *  linux/kernel/exit.c * *  (C) 1991  Linus Torvalds */#include <errno.h>#include <signal.h>#include <sys/wait.h>#include <linux/sched.h>#include <linux/kernel.h>#include <linux/tty.h>#include <asm/segment.h>int sys_pause(void);int sys_close(int fd);void release(struct task_struct * p){	int i;	if (!p)		return;	for (i=1 ; i<NR_TASKS ; i++)		if (task[i]==p) {			task[i]=NULL;			free_page((long)p);			schedule();			return;		}	panic("trying to release non-existent task");}static inline int send_sig(long sig,struct task_struct * p,int priv){	if (!p || sig<1 || sig>32)		return -EINVAL;	if (priv || (current->euid==p->euid) || suser())		p->signal |= (1<<(sig-1));	else		return -EPERM;	return 0;}static void kill_session(void){	struct task_struct **p = NR_TASKS + task;		while (--p > &FIRST_TASK) {		if (*p && (*p)->session == current->session)			(*p)->signal |= 1<<(SIGHUP-1);	}}/* * XXX need to check permissions needed to send signals to process * groups, etc. etc.  kill() permissions semantics are tricky! */int sys_kill(int pid,int sig){	struct task_struct **p = NR_TASKS + task;	int err, retval = 0;	if (!pid) while (--p > &FIRST_TASK) {		if (*p && (*p)->pgrp == current->pid) 			if (err=send_sig(sig,*p,1))				retval = err;	} else if (pid>0) while (--p > &FIRST_TASK) {		if (*p && (*p)->pid == pid) 			if (err=send_sig(sig,*p,0))				retval = err;	} else if (pid == -1) while (--p > &FIRST_TASK)		if (err = send_sig(sig,*p,0))			retval = err;	else while (--p > &FIRST_TASK)		if (*p && (*p)->pgrp == -pid)			if (err = send_sig(sig,*p,0))				retval = err;	return retval;}static void tell_father(int pid){	int i;	if (pid)		for (i=0;i<NR_TASKS;i++) {			if (!task[i])				continue;			if (task[i]->pid != pid)				continue;			task[i]->signal |= (1<<(SIGCHLD-1));			return;		}/* if we don't find any fathers, we just release ourselves *//* This is not really OK. Must change it to make father 1 */	printk("BAD BAD - no father found\n\r");	release(current);}int do_exit(long code){	int i;	free_page_tables(get_base(current->ldt[1]),get_limit(0x0f));	free_page_tables(get_base(current->ldt[2]),get_limit(0x17));	for (i=0 ; i<NR_TASKS ; i++)		if (task[i] && task[i]->father == current->pid) {			task[i]->father = 1;			if (task[i]->state == TASK_ZOMBIE)				/* assumption task[1] is always init */				(void) send_sig(SIGCHLD, task[1], 1);		}	for (i=0 ; i<NR_OPEN ; i++)		if (current->filp[i])			sys_close(i);	iput(current->pwd);	current->pwd=NULL;	iput(current->root);	current->root=NULL;	iput(current->executable);	current->executable=NULL;	if (current->leader && current->tty >= 0)		tty_table[current->tty].pgrp = 0;	if (last_task_used_math == current)		last_task_used_math = NULL;	if (current->leader)		kill_session();	current->state = TASK_ZOMBIE;	current->exit_code = code;	tell_father(current->father);	schedule();	return (-1);	/* just to suppress warnings */}int sys_exit(int error_code){	return do_exit((error_code&0xff)<<8);}int sys_waitpid(pid_t pid,unsigned long * stat_addr, int options){	int flag, code;	struct task_struct ** p;	verify_area(stat_addr,4);repeat:	flag=0;	for(p = &LAST_TASK ; p > &FIRST_TASK ; --p) {		if (!*p || *p == current)			continue;		if ((*p)->father != current->pid)			continue;		if (pid>0) {			if ((*p)->pid != pid)				continue;		} else if (!pid) {			if ((*p)->pgrp != current->pgrp)				continue;		} else if (pid != -1) {			if ((*p)->pgrp != -pid)				continue;		}		switch ((*p)->state) {			case TASK_STOPPED:				if (!(options & WUNTRACED))					continue;				put_fs_long(0x7f,stat_addr);				return (*p)->pid;			case TASK_ZOMBIE:				current->cutime += (*p)->utime;				current->cstime += (*p)->stime;				flag = (*p)->pid;				code = (*p)->exit_code;				release(*p);				put_fs_long(code,stat_addr);				return flag;			default:				flag=1;				continue;		}	}	if (flag) {		if (options & WNOHANG)			return 0;		current->state=TASK_INTERRUPTIBLE;		schedule();		if (!(current->signal &= ~(1<<(SIGCHLD-1))))			goto repeat;		else			return -EINTR;	}	return -ECHILD;}